The present invention relates to digital networks, and in particular, to delivering and managing multicast traffic over wireless local area networks.
Digital networks have rapidly become the backbone of many enterprises, small and large. Such networks are used for handling many different kinds of traffic. One type of traffic becoming increasingly important is Multicast traffic, which is used to carry media streams such as video, among others.
Multicast by definition is traffic sent from one source to multiple destinations. As an example, if twenty users subscribe to the same video stream, only one multicast stream is transmitted from a media server through the network to multiple destination, rather than twenty separate unicast streams.
Protocols such as IGMP and MLD are known in the art for managing multicast membership in IPV4 and IPV6 networks respectively. These protocols for managing multicast membership in the network, rely upon reliable delivery of the underlying multicast packets. Where IGMP is a separate protocol in the IPv4 world, MLD is a component of the IPv6 suite. MLDv1 is similar to IGMPv2, and MLDv2 is similar to IGMPv3. MLD is described in RFC 3810.
Wireless networks, and multicast distribution over wireless networks such as wireless local area networks (WLANs) introduce a host of new problems to multicast distribution. On the wired network, all packets travel at the same speed, and the CSMA/CD nature of wired Ethernet networks carries with it a high degree of reliability. On WLANs, however, multicast packets are sent at much lower data rates, in comparison to unicast packets, to help insure delivery. Multicast packets are also sent using UDP, a connectionless protocol, with limited error recovery mechanisms.
Many WLAN systems deliver multicast traffic over WLANs by converting the multicast packets to unicast at Layer 2, such as at an access point (AP). While this allows the converted multicast packets to be transmitted at much higher data rates, issues still exist with respect to MLD control-plane traffic such as Joins and Queries.
Inconsistent IPV6 multicast group membership, as an example, results in multicast to unicast conversions not happening for interested clients, or wasted bandwidth in sending multicast streams to clients that are not interested in the multicast group.
What is needed is a way to improve handling of packets related to Multicast membership management protocols like MLD in wireless portions of a network.